The present invention relates to an air spinning frame as well as to a method for the operation of an air spinning frame.
Air spinning frames comprise a large number of spinning places. Thereby, in each spinning place, a thread is spun from a supplied longitudinal fibre formation. The spinning procedure is affected by means of the drafting unit in which the fibre amount per unit of length is reduced by the drafting process. For this, the drafting unit usually comprises three pairs of rollers, arranged one behind the other, whose circumferential speed increases from pair of rollers to pair of rollers. Thereafter, the longitudinal fibre formation, refined in such a way, is spun into a thread in a spinning nozzle by twisting. Air spinning frames use the air spinning method for the thread formation, i.e., the thread formation takes place by air twisting. Thereafter, the thread is drawn off by means of a further pair of rollers and finally wound onto a yarn package. This yarn package is preferably driven by means of a friction roller, which itself is connected with a motor.
After a thread break or a required change of the yarn package, the spinning procedure must again be started (pieced) newly. For a production interruption that is as short as possible, it is required that the pairs of rollers of the drafting unit and of the draw-off means, as well as also of the friction roller, run-up very fast and/or practically instantaneous. A quasi-instantaneous run-up does mean that the operating speed must be reached within a very short time, for example, within 1 to 2 seconds. Beyond that, with a fast run-up, a certain quality of piecing is thereby also ensured.
In the U.S. patent application, US 2001/0042365 A1 (PAWELETZ, Anton; BAHLMANN, Bernd; BOCK, Erich; SCHULLER, Edmund), a spinning frame with several individual drives is disclosed, where a synchronous motor is applied. One of the motors thereby serves as “Lead motor”, so that from its speed, by means of a control means/regulation means, the other motors are controlled accordingly. Such permanently excited motors are, however, not very common because of the accommodation of the magnet.
In the disclosure EP 1 205 588 A1 (Maschinenfabrik Rieter AG), a spinning frame is disclosed, in which the drafting unit of a spinning place is at least partly controllable and drivable independent of the drafting unit of the other spinning places, whereby for each spinning place, at least one sensor means is provided. A relatively complex regulation means for each spinning place is, however, necessary, since the run-up method of the motors must be monitored indirectly by means of the mentioned sensor means.